1. Field of the Invention
This invention relates to a small-enveloped, single-acting, hydraulically-operated, reciprocating, deep-well, fluid-extraction pump and its mode of operation. More particularly, this invention relates to a small-enveloped, single-acting, hydraulically-operated, reciprocating, deep-well, fluid-extraction pump having an above-ground installation of its motor-fluid generator and of its control valving, with the hydraulically-operated, deep-well pump comprising a compound, stepped piston that is reciprocably mounted within a cylinder which in turn is divided into individual pressure chambers, and to the mode of operation of said hydraulically-operated, deep-well pump.
2. General Background
In designing fluid-extraction pumps for deep wells, some factors should always be taken into consideration. The fluid-extraction pump should be simple in design and should include a minimum number of parts to be capable of being fit into small well bores. In addition, the pump should have a relatively short physical length to be passed through curved sections of well casing and into angular wells relatively easily. Different components of the fluid-extraction pump should be designed under one common goal: provision of a very long service life for the pump. A pump with these desirable attributes would most probably withstand early malfunction and breakage of various component parts thereof. It is also desirable that the pump would use energy as efficiently as possible and that power requirement for fluid extraction are considerably less than could be expected for proportionally deeper wells.
3. Description of the Prior Art
In the prior art, different types of pumps have been used in an attempt to solve the problems faced in deep-well, fluid extraction. Some devices have been repeatedly used. Reciprocating, deep-well pumps, used for the extraction of petroleum fluids, brine or water, have been designed to fit into large bore wells and are normally connected to surface machinery through an elongate operating puller, commonly known as "sucker rod". The so-called "sucker rod" pumps are single-acting pumps that have proven to be beneficial for pumping straight and truly vertical wells. However, "sucker rod" pumps are limited to straight wells and cannot be operated in bowed wells, slanted wells, horizontal wells, and/or angular wells.
Meanwhile, high-force, low-speed, mechanical equipment, including but not limited to pumping jacks, have been used to reciprocate pumping mechanisms. These high-force, low-speed, mechanical equipment are costly and necessitate a considerable upkeep. A high maintenance cost and considerable upkeep of these mechanical equipment are only justifiable in high-output wells since the output of mechanically-operated pumps is limited to at most one-sixth of natural frequency of an elastic interaction of the sucker rod and bulk modulus of any pumped fluid.
Hydraulically-operated, single-acting, positive-displacement pumps are a different type of pump wherein a power or pumping stroke and a return or recharge stroke is accomplished by a combination of hydraulic pressure and spring pressure or by a combination of hydraulic pressure and compressed gas pressure. Most hydraulically-operated pumps utilize a considerable volume of effective operating fluid and are limited to number of pumping cycles per minute due to cyclic operations of pressurization and recovery, the expansion and contraction of the pressure line, the fluid friction during downhole and return-flow cycles, and fluid viscosity.
Energy transfer of fluid power is utilized to reciprocate hydraulically-operated, single-acting or double-acting pumps. Hydraulic power that is generated by an above-the-ground, central, power station is conducted to the pumping unit through at least one tube, with each tube acting alternatively as a conductor of pressurized fluid. The fluid flow of any motor fluid is selectively switched by valving that is interconstructed into each power piston. Fluid passages and valves for any motor fluid, as well as for any pumped fluid, dictate certain minimum sizes. The minimum sizes, in turn, define a minimum envelope for a down-hole pump. Establishment of minimal sizes may not be applicable to small-bore wells and may only have to be limited to large-bore wells. The miniaturization of the valving, as well as constant existence of contaminants (including but not limited to sand) in the pumped fluid, have made previous, hydraulically-operated, single-acting or double-acting pumps unreliable.
In addition, a large number of patents have been issued which have attempted to solve one or more of the above issues or some other similar problems related to deep-well, fluid extraction. A summary of some of the more relevant of said patents follow.
Roeder, U.S. Pat. No. 4,214,854, registered on Jul. 29, 1980, (referred to as '854) and U.S. Pat. No. 5,104,296, registered on Apr. 14, 1992, (referred to as '296), for example, discuss hydraulically-actuated pump assemblies. In '854, Roeder patents a mechanically-actuated valve assembly contained within a piston of an engine of a downhole hydraulically-actuated pump assembly, the engine being reciprocatingly connected to a production pump, and arranged with respect to various different flow passageways such that flow of power fluid downhole to and through the engine, while production fluid and spent power fluid are conducted uphole to the surface of the ground, forces the engine piston to reciprocate. The valve assembly includes a control rod and a valve element concentrically arranged with respect to one another and to the engine piston. Reciprocation of the control rod causes the valve element to reciprocate respective to the engine piston. In '296, Roeder patents a pump end of a hydraulically actuated downhole pump assembly, powered by a fluid that is pumped downhole to an engine end thereof. The pump end is connected to a source of formation fluid so that the engine end drives the pump end which in turn lifts produced fluid to the surface of the ground. The pump end has a pump barrel within which a pump piston is reciprocatingly received in sealed relationship. The engine end has an outer engine barrel within which an annular valve element is reciprocatingly received in sealed relationship. The valve element moves up and down between two positions of operation while an engine piston reciprocates within the annular valve element and, thus, aligns various flow passageways in a manner to alternately apply power fluid to appropriate sides of the piston and valve element to force the engine piston to reciprocate.
Roeder, U.S. Pat. No. 4,544,335, issued on Oct. 1, 1985, patents a downhole hydraulically actuated pump assembly, comprising: a power piston actuating a production plunger.; a valve means concentrically arranged within the power piston; and a stationary, hollow, valve-control rod extending through the power piston and through the valve means and having a lower marginal end which terminates within the production plunger. Power fluid flows through the valve-control rod and to the valve means. Means on the valve-control rod actuates the valve means between two alternant positions so that power fluid is applied to bottom face of the power piston, causing the power piston to reciprocate upward; and thereafter, the valve-control rod causes the valve means to shift to the other position, whereupon spent power fluid is exhausted.
Canens, U.S. Pat. No. 4,925,374, issued on May 15, 1990, discusses a sub-surface hydraulically operated engine for reciprocating an oilwell pumping unit. The engine includes confined hydraulic fluid means for actuating a reversing valve and its lifter in order to change the upstroke motion to downstroke motion and vice versa.
Reese, U.S. Pat. No. 4,383,803, was issued on May 17, 1983. Reese patents a device for lifting liquid from boreholes, said device comprising: a pump being located downhole near production formation and consisting of a fluid-actuated, double-action piston. The pump is connected by fluid pressure lines to a source of fluid pressure disposed above ground and a switching valve is connected to provide fluid pressure to alternate sides of the piston to effect reciprocation thereof.
Bennett, U.S. Pat. No. 4,295,801, was issued on Oct. 20, 1981. Bennett patents a small-diameter, fluid-powered, submersible, sampling pump including an elongated, cylindrical body formed by: a pair of hollow chambers of a motor piston; and a centrally-disposed, control-valve, block assembly being located on opposite sides of the motor piston chambers and joined thereto and containing, in axial alignment with the motor piston, a spool pilot valve and a spool fluid-distribution valve. The spool pilot valve, which is constructed to obviate stalling during its reciprocation under the impress of a power fluid directed thereto and functions to control the shifting of the distribution valve to which it is internally connected within the valve block assembly, comprises: a valve housing defining a large, central, piston chamber; a relatively small bore extending axially inwardly from one end of the valve housing and into communication with the large, central, piston chamber; and a larger bore of smaller diameter than the central, piston chamber extending axially into the opposite end of the valve housing into communication with the central, piston chamber. A small piston is slidably positioned in the relatively small bore, a larger piston in the larger bore and a largest piston in the central piston chamber. A power fluid charging port communicates with the central piston chamber through the valve housing, such that sealing means on the largest piston in the central piston chamber allows power fluid to bleed from the power fluid charging port to opposite sides of the largest piston when the sealing means is directly aligned with the power fluid charging port.
Hydraulically-operated, deep-well, fluid-extraction pumps discussed above and existing in prior art have several major disadvantages in common which are intended to be avoided in the present invention. The hydraulically operated deep well pumps of previous art have the directional fluid flow control valve, installed within the mechanism of pump piston, in order to reduce the time required for the travel of pressure shock wave, in the power line(s) (e.g. 1530 m/sec), at the cost of high failure rate of the built-in, directional-flow, control valve, in sand laden ambient.
Therefore, it is desirable to develop a hydraulically-operated, deep-well, fluid-extraction pump that would overcome the above defects while performing any required task.